The valley and its recipes
A coast, a winding river, hills and woodland from one seed; then caves, cliffs, gorges and terraces carved by a recipe before anybody arrives.
Every valley comes out of a number. terrain::generate draws a coast, a river that meanders from the hills to the sea, four to nine hills, a plain, woodland, a stone outcrop, clay on the flats and an offshore island from six seeded noise fields, and freezes that natural surface so the city can always measure its own made ground against it. The founders land in a clearing near the middle, clear of the river and the cliffs.
The engine adds a recipe on top: the same site plus a list of features, each a few numbers and a way of moving ground. Anchors are named (the river head, the highest peak, the ford, the founding spot, a fraction of the map) so a recipe survives a change of seed. The Sculptor enforces two rules for every feature: only nature is moved, never built fabric, roads, the sea or the river, and the natural surface follows, so a gorge carved at birth is the hillside the city measures against.
The presets are plain valley, karst valley, alpine gorge and terraced highlands; the rules reference lists their features. In the native viewer the terrain tab carves features into a live valley, keeping off everything the town is using, and drafts a recipe from what you tried.
What to look for. Pick material and the whole site is what it is made of: grass, dirt, stone faces, water. Switch to the water lens and the drainage the next page describes is already there before a drop has fallen: the river in its channel, the hollows that will hold lakes.
In the code: crates/sim/src/terrain.rs crates/engine/src/worldgen/mod.rs crates/engine/src/worldgen/features.rs · playground: land